Elongate medical devices such as introducer sheaths are commonly used in medical procedures for gaining access to a subcutaneous site within a human body by providing a hollow pathway between the surface of the skin and the target site. For example, catheter insertion procedures such as peripherally inserted central catheter placement or midline catheter placement commonly utilize introducer sheaths for gaining access to the lumen of a blood vessel. A typical introducer sheath is made from a thin hollow plastic tubular structure with a hollow opening on the insertion or distal end and a hemostatic valve on the proximal end. Introducer sheaths come in a variety of shapes and sizes, and medical professionals typically select a shape and size corresponding to the type of procedure being performed and the access site being targeted. Introducer sheaths also include a dilator with a tapered distal end for accommodating a smooth transition as the sheath is advanced through a venipuncture site and into the lumen of the blood vessel. The introducer sheath and dilator are typically packaged together as a dilator sheath assembly.
FIGS. 1A-1E show an exemplary prior art technique for inserting a dilator sheath assembly into the blood vessel of a patient 10. A venipuncture is performed with a percutaneous introducer needle 50 by inserting the needle 50 into the skin 12 at an approximately 30-45 degree angle with the surface of the skin. The needle 50 is advanced through tissue 14 until the tip of the distal end 58 of the needle 50 enters the lumen of the target blood vessel 16. Detection of flashback indicates that the tip of the needle has entered the lumen of the blood vessel and that the tip of the needle 50 is properly positioned. As shown in FIG. 1B, once the needle is properly positioned with fluid access to the target blood vessel 16, a guide wire 60 can be inserted into the proximal end 52 of the needle, advanced to the distal end 58, advanced out of the needle tip and into the blood vessel 16. With the guide wire 60 positioned within the blood vessel 16, the needle 50 can be retracted off the guide wire 60, and access is maintained via the guide wire 60 as shown in FIG. 1C.
Now with reference to FIG. 1D, a small nick 18 is made in the skin 12 adjacent to the guide wire 60 at the venipuncture site using a scalpel 20. By nicking the skin, an opening 18 is created in the skin 12 for accommodating advancement of the dilator sheath assembly 22 or other elongate medical device over the guide wire 60 and into the blood vessel 16. Without nicking the skin, the medical professional performing the procedure may encounter significant resistance while attempting to advance the dilator sheath assembly 22 through the skin 12. Further, if the venipuncture site is too small, the opening 28 of the sheath 26 which coaxially surrounds the dilator 24 may curl back or “fish mouth” as the medical professional attempts to advance it through the skin 12, causing damage to the sheath 26 and possibly injury to the patient 10.
More generally, nicking the skin with a scalpel is common for procedures facilitating subcutaneous access and insertion of a variety of elongate medical devices. For example, certain angioplasty catheters for treatment for peripheral artery disease are designed for direct insertion into the arterial system without the need for a dilator sheath. Or, for example, for endovascular laser treatment, the skin may be nicked to facilitate advancing a procedure sheath or an optical fiber.
In the technique described above, medical professionals typically use a scalpel to nick the skin prior to inserting the elongate medical device, such as a dilator sheath assembly. However, problems arise when using a scalpel to perform the step of nicking the skin. For example, creating a small nick that is accurately close to the venipuncture site requires precise maneuvering of the scalpel to avoid damaging the guide wire. Medical professionals are warned against contacting the sharp side of the scalpel with the guide wire since it is fragile and can be easily damaged. A damaged guide wire may require removal from the patient or restarting the procedure with a new guide wire, further increasing risk to the patient. Further, it is difficult to consistently create a small nick in the skin of appropriate size. Skin nicks that are too small will not facilitate insertion of the elongate medical device. Conversely, excessively large nicks may cause unnecessary bleeding and scaring in the patient. Still further, including a scalpel as a separate component in an access kit requires more space in the kit and adds inefficiency to the procedure. Therefore, there is a need for an improved device, method and assembly for accurately, consistently and efficiently nicking the skin without risking damage to the guide wire, and while minimizing risk of injury to the patient.